Each year, about one million women are diagnosed with breast cancers in the world, which is the second leading cause of death for women. However, it can effectively improve the survival rate of patients by treating tumors at the early stage. Therefore, it is an important issue to detect the breast cancer early for the health of women.
Due to the advantages of non-invasion, non-contact, passivity, non-radiation and the ability of detecting the slight variations of temperature caused by neovascularization, Infrared imaging technique has been developed and employed for assessing chemotherapy treatment response. Serving as a medical imaging modality, the Infra-red (IR) image reveals the heat distribution on the surface of the human body. Cancerous tissues tend to have a higher temperature signature than their surrounding normal tissues, and for this reason, IR image has long been studied in hope to serve as an indicator for cancerous breast tissues. Nevertheless, the usefulness of IR images in detecting breast cancers remains controversial due to the physiological and environmental influence on the skin temperature distribution, and most importantly, there are no objective methods to quantitatively analyze lesion malignancy.
In the prior art, some methods have been reported to detect breast cancers or to assess treatment results of breast cancer chemotherapy using the IR image. These methods can be classified into two general categories, namely cross-sectional and longitudinal approaches. The cross-sectional approaches are mainly based on the comparison between the temperature of the normal area and that of the cancerous area of the breast. Although the breast area with tumors is expected to be higher than that of the normal breast area, it does not necessarily mean that the high temperature area in IR images corresponds to the tumor region (Lawson R., “Implications of surface temperatures in the diagnosis of breast cancer,” Canadian Medical Association Journal, p. 309-310, 1956, Lawson R. N., Chughtai M. S., “Breast Cancer and Body Temperature,” Canadian Medical Association Journal, p. 68-70, 1963 and Stark A. M., Way S., “The use of thermovision in the detection of early breast cancer,” Cancer, p. 1664-1670, 1974). Therefore, it is too arbitrary to use the heat pattern acquired at a single time point as the basis to determine if there is a tumor in a breast.
Alternatively, the longitudinal approaches attempt to determine the malignancy of breast tissues based on the variation of heat pattern over several time points. The general idea is the heat pattern of each person remains roughly unchanged under similar physiological and environmental conditions. It has been observed that the heat patch in the IR image may shrink or even disappear in what seems like a direct correlation to the tumor blood vessels breaking down and eventually disappear as treatment progress (Zylberberg B., Salat-Baroux J., Ravina J. H., et al., “Initial chemoimmunotherapy in inflammatory carcinoma of the breast,” Cancer, p. 1537-1543, 1982). However, a longitudinal approach may have the noisy variations caused by the physiological and environmental factors at different time points. Although the influence of such environmental variables as temperature, humidity, and so on, may be minimized through deliberate control, these factors could still disturb the IR intensity fluctuation and affects the quantitative estimation of IR intensity change along the time. To quantitatively analyze this subjective visual judgment on the change of a breast tumor, each breast is divided into four parts and compared with the temperature distribution of each pair of corresponding parts (Ng E. Y. K., Fok S. C., Peh Y. C., et al., “Computerized detection of breast cancer with artificial intelligence and thermograms,” Journal of Medical Engineering & Technology, p. 152-157, 2002). The potential deficiency of this approach lies in the fallacious implicit assumption that the two breasts under the normal condition have the same temperature distributions.
In addition, prior to the present invention, the multiple-spectrum IR information is employed in a longitudinal approach at the same time in order to detect and quantify the breast cancer information collected under minimal physiological and environmental effects. By combining different energies received in the IR images of different spectrums, this approach offers an opportunity to further reduce the influence of the physiological and environmental factors. The blind source separation algorithm using two satellite-grade infrared cameras demonstrated that it is likely to detect breast cancer based on a pair of MIR and LIR breast images (Szu H., Miao L. and Qi H., “Thermodynamic free-energy minimization for unsupervised fusion of dual-color infrared breast images,” SPIE, Florida, 2006). Since this algorithm mainly counts on the minute difference between the vectors, i.e., (MIR, LIR), of the cancerous and normal tissues, further investigation is required to attain a sufficient signal-to-noise ratio for this idea to be applied in a clinical setting.
According to the present invention, applicants have departed from the conventional wisdom, and had conceived and implemented a new longitudinal approach to estimate the heat pattern change on the breast skin with IR photon information from a pair of MIR and LIR cameras, rather than directly estimating the likelihood that each pixel contains cancerous tissue. The effects of chemotherapy on breast cancer are effectively traced and evaluated by using this method. The invention is briefly described as follows.